JP2022171139A - Manufacturing method and manufacturing facility for cold-rolled steel sheet - Google Patents

Abstract

To provide a manufacturing method and manufacturing facility for a cold-rolled steel sheet which enable silicon steel sheets to be rolled stably under low environmental load.SOLUTION: A manufacturing method for a cold-rolled steel sheet according to the present invention uses a full-width heating apparatus that heats a steel sheet over the whole area in a width direction, of the steel sheet, an edge portion heating apparatus that heats an end portion in the width direction, of the steel sheet, and a cold rolling mill that rolls a steel sheet and is arranged at a downstream side in a rolling direction with respect to the full-width heating apparatus and the edge portion heating apparatus, the manufacturing method includes a step of heating a steel sheet using the full-width heating apparatus and the edge portion heating apparatus in such a manner that a temperature of the end portion in the width direction, of the steel sheet is higher than a temperature of a central portion in the width direction, of the steel sheet, at an entry side of the cold rolling mill.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method and equipment for manufacturing cold-rolled steel sheets.

Conventionally, in cold rolling, a single-stand reverse mill such as a Sendzimir mill or a tandem mill with multiple stands has been used. There are many cases. By the way, in the cold rolling of a silicon steel sheet (electromagnetic steel sheet) having a high Si content, when the steel sheet temperature is low, brittle fracture of the steel sheet tends to occur. At this time, there are cases where the steel sheet breaks at the ends in the width direction or at the center in the width direction. is valid. Against this background, a method has been proposed for suppressing breakage of the silicon steel sheet by heating the silicon steel sheet before cold rolling. For example, Patent Literature 1 describes a method of heating the width direction end portion of a steel sheet so as to reach a designated target temperature on the entry side of the rolling mill. Further, Patent Document 2 describes a method of uniformly heating and rolling a steel plate over its entire area.

JP 2012-148310 A JP 2011-79025 A

As described above, techniques for suppressing the occurrence of brittle fracture during cold rolling of silicon steel sheets with a high Si content have been proposed. However, with the technique of heating only the widthwise end portions of the steel sheet, brittle fracture may occur at the widthwise central portion due to the low temperature of the steel sheet near the widthwise central portion. In addition, there is a possibility that the technology that heats the steel plate uniformly across the entire width of the steel plate is heating the entire steel plate with more energy than necessary, and there is room for review from the perspective of SDGs (Sustainable Development Goals). It is believed that there is.

The present invention has been made in view of the above problems, and an object thereof is to provide a cold-rolled steel sheet manufacturing method and manufacturing equipment capable of stably rolling a silicon steel sheet with low environmental load. .

In order to achieve the above object, the inventors of the present invention conducted extensive research and found that the fracture suppression temperature (steel plate temperature at which the fracture suppression effect is high) is higher at the widthwise ends than at the widthwise central portion. I found out. Therefore, the inventors combined a full-width heating device that heats the entire width of the steel plate and an edge heating device that heats the ends of the steel plate in the width direction, and appropriately control the outputs of both. However, we thought that it was very effective in terms of fracture suppression and environment, and came up with the following invention.

A method for manufacturing a cold-rolled steel sheet according to the present invention includes a full width heating device that heats the steel plate over the entire width direction of the steel plate, an edge portion heating device that heats the width direction end portion of the steel plate, the full width heating device, and A method for manufacturing a cold-rolled steel sheet using a cold rolling mill that rolls the steel sheet, which is arranged on the downstream side in the rolling direction with respect to the edge heating device, wherein at the entry side of the cold rolling mill The method includes a step of heating the steel sheet using the full-width heating device and the edge heating device so that the temperature of the widthwise end portions of the steel plate is higher than the temperature of the widthwise central portion of the steel plate.

In the method for manufacturing a cold-rolled steel sheet according to the present invention, in the above-described invention, the temperatures of the widthwise central portion and the widthwise end portions of the steel sheet on the entry side of the cold rolling mill change according to the Si content of the steel sheet. It is characterized by

In the method for manufacturing a cold-rolled steel sheet according to the present invention, in the above-described invention, the temperature at the widthwise central portion and the widthwise end portion of the steel sheet on the entry side of the cold rolling mill changes according to the following formula ( It is characterized by being the temperature calculated by 1) and (2).

A method for manufacturing a cold-rolled steel sheet according to the present invention is characterized in that, in the above-described invention, a full-width heating step of heating the steel sheet over the entire width direction of the steel sheet by the full-width heating device; and a rolling step of rolling the steel plate by the cold rolling mill are performed in this order.

A method for manufacturing a cold-rolled steel sheet according to the present invention is, in the above-described invention, an edge portion heating step of heating the width direction end portions of the steel plate with the edge portion heating device, and heating the entire width direction of the steel plate with the full width heating device. A full-width heating step of heating the steel plate and a rolling step of rolling the steel plate with the cold rolling mill are performed in this order.

The cold-rolled steel sheet manufacturing equipment according to the present invention includes a full width heating device that heats the steel plate over the entire width direction of the steel plate, an edge portion heating device that heats the width direction end portion of the steel plate, the full width heating device, and and a cold rolling mill for rolling the steel sheet, which is arranged downstream in the rolling direction with respect to the edge heating device, wherein the full width heating device and the edge heating device are located on the entry side of the cold rolling mill. In the above, the steel plate is heated so that the temperature of the widthwise end portions of the steel plate is higher than the temperature of the widthwise center portion of the steel plate.

In the cold-rolled steel sheet manufacturing equipment according to the present invention, in the above invention, the full width heating device and the edge heating device are arranged at the center of the width direction of the steel plate on the entry side of the cold rolling mill according to the Si content of the steel plate. It is characterized by changing the temperature of the part and the width direction end part.

In the cold-rolled steel sheet manufacturing facility according to the present invention, in the above invention, the full-width heating device and the edge heating device set the temperature of the widthwise central portion and the widthwise end portion of the steel sheet on the entry side of the cold rolling mill. is heated to a temperature calculated by the following formulas (1) and (2), which varies depending on the Si content α.

The cold-rolled steel sheet manufacturing equipment according to the present invention is characterized in that, in the above invention, the full width heating device and the edge heating device are installed at a position within 10 m from the entry side of the cold rolling mill. do.

The cold-rolled steel sheet manufacturing equipment according to the present invention is characterized in that, in the above invention, the full-width heating device is a solenoid induction heating device.

The cold-rolled steel sheet manufacturing equipment according to the present invention is characterized in that, in the above invention, the full width heating device and the edge heating device are arranged in this order from the upstream side of the cold rolling mill in the rolling direction. .

The cold-rolled steel sheet manufacturing equipment according to the present invention is characterized in that, in the above invention, the edge portion heating device and the full width heating device are arranged in this order from the upstream side of the cold rolling mill in the rolling direction. .

According to the cold-rolled steel sheet manufacturing method and manufacturing equipment according to the present invention, a silicon steel sheet can be stably rolled with low environmental load.

FIG. 1 is a schematic diagram showing the configuration of a cold-rolled steel sheet manufacturing facility according to an embodiment of the present invention. FIG. 2 is a diagram showing the results of evaluating the temperature dependence of bending crack resistance of a silicon steel sheet. FIG. 3 is a diagram showing estimation results of the steel sheet temperature necessary for suppressing brittle fracture according to the Si content of the steel sheet. FIG. 4 is a graph showing the results of evaluating the temperature dependence of edge crack resistance of a silicon steel sheet. FIG. 5 is a diagram showing estimation results of the steel sheet temperature necessary for suppressing edge cracking according to the Si content of the steel sheet.

BEST MODE FOR CARRYING OUT THE INVENTION A method and equipment for manufacturing a cold-rolled steel sheet according to an embodiment of the present invention will be described below with reference to the drawings. Components in the embodiments shown below include components that can be easily replaced by those skilled in the art, or components that are substantially the same.

〔Constitution〕
First, referring to FIG. 1, the configuration of a cold-rolled steel sheet manufacturing facility according to an embodiment of the present invention will be described.

FIG. 1 is a schematic diagram showing the configuration of a cold-rolled steel sheet manufacturing facility according to an embodiment of the present invention. As shown in FIG. 1, a cold-rolled steel sheet manufacturing facility (hereinafter abbreviated as "manufacturing facility") according to one embodiment of the present invention is a continuous tandem rolling line having a plurality of stands. Device 2, looper 3, full width heating device 4, edge heating device 5 (hereinafter referred to as "heating device 6" when referring to both full width heating device 4 and edge heating device 5), thermometer (plate temperature A measuring device) 7 , a cold tandem rolling mill 8 , a cutting machine (cutting device) 9 and a tension reel 10 are provided.

The payoff reel 1 is a device for paying out the steel plate S. A manufacturing facility may have a plurality of payoff reels 1 . In this case, a plurality of payoff reels pay out different steel sheets S respectively.

The joining device 2 forms a joined steel plate by joining the tail end of the steel plate (leading material) paid out first from the payoff reel 1 and the leading end of the steel plate (following material) paid out later from the payoff reel 1. It is a device that A laser welder is preferably used as the joining device 2 .

The looper 3 is a device that stores the steel plate S so that cold rolling by the cold tandem rolling mill 8 can be continued until the steel plates are joined together by the joining device 2 (until joining is completed). .

The full-width heating device 4 is a device that heats the steel plate S over the entire width direction and rolling direction (longitudinal direction) of the steel plate S. In addition, the full width heating device 4 is set so that the temperature of the central portion in the width direction of the steel sheet S at the entry side of the cold tandem rolling mill 8 is calculated by the following formula (1), and the temperature corresponding to the Si content of the steel sheet S It is desirable to heat the steel plate S so that it becomes _TC . Thereby, the brittle fracture of the steel sheet S can be effectively suppressed.

The edge portion heating device 5 is a device that heats the edge portion (end portion in the width direction) of the steel sheet S over the entire rolling direction. In the edge heating device 5, the temperature of the edge on the entrance side of the cold tandem rolling mill 8 is a temperature _TE according to the Si content of the steel sheet S calculated by the following formula (2). It is desirable to heat the edges in such a way that At this time, it is also necessary to consider the temperature of the edge portion, which rises due to the heating of the steel plate S by the full-width heating device 4 . As a result, edge cracks in the steel sheet S can be effectively suppressed.

The thermometer 7 is a device for measuring the surface temperature of the steel sheet S. The thermometer 7 is desirably installed near the entry side of the cold tandem rolling mill 8 . However, in practice, instead of using the steel plate temperature measured by the thermometer 7 as it is, a value that compensates for the steel plate temperature that decreases between the thermometer 7 and the entry side of the cold tandem rolling mill 8 is used. By doing so, it will be put into practical use.

The cold tandem rolling mill 8 is a device that cold-rolls the steel sheet S in order to make the thickness of the steel sheet S heated by the full-width heating device 4 and the edge heating device 5 a target thickness. In this embodiment, the cold tandem rolling mill 8 has five stands, but the number of stands is not particularly limited. In addition, in the present embodiment, the cold tandem rolling mill 8 has a form called 4Hi having four rolls in one stand, but it is not limited to this, and other forms such as 6Hi are also applicable. can do.

The cutting machine 9 is a device for cutting the steel plate S after cold rolling.

The tension reel 10 is a device for winding the steel plate S cut by the cutting machine 9 . The form of the tension reel 10 is not limited, and may be, for example, a carousel tension reel. Also, the manufacturing facility may have a plurality of tension reels 10 . In this case, the plurality of tension reels 10 wind up the plurality of steel plates S continuously.

Devices included in the manufacturing facility are not limited to the devices described above. In the manufacturing equipment, the heating device 6 (the order of the full width heating device 4 and the edge heating device 5 is not limited) and the entry side of the cold tandem rolling mill 8 are arranged in this order within 10 m (more preferably adjacently arranged). It is good if there is Therefore, the rolling mill may be a reverse rolling mill instead of a tandem rolling mill. In this case, the heating device 6 and the rolling mill are arranged in this order in the first pass. Further, the cold rolling process and the pickling process, which is the preceding process, can be performed continuously, and a pickling device for pickling the steel sheet S is arranged between the looper 3 and the cold tandem rolling mill 8. You may

[Heating process]
Next, a heating process of the steel sheet S by the heating device 6, which is a feature of the manufacturing method of the cold-rolled steel sheet according to one embodiment of the present invention, will be described. Although the specific heating means of the heating device 6 is not particularly limited, the case where the heating device 6 is an induction heating device will be described below as an example. Further, the full-width heating device 4 may be either a solenoid type or a transverse type induction heating device. Moreover, although the heating device 6 heats at least one of the upper surface and the lower surface of the steel plate S, it is more preferable to heat both the upper surface and the lower surface.

In the heating step of the steel sheet S of the present embodiment, the heating device 6 controls the temperature of the steel sheet S measured by the thermometer 7, the target temperature of the steel sheet S on the delivery side of each of the full width heating device 4 and the edge heating device 5, and the temperature of the steel plate S. The target temperature of the heating device 6 is determined based on the time for S to pass through the heating device 6 (that is, the heating time) and the plate thickness of the steel plate S. The target temperature of the steel sheet S heated by the heating device 6 is a temperature that takes into account the distance between the thermometer 7 and the heating device 6 and the distance between the thermometer 7 and the cold tandem rolling mill 8. Must be set. For example, when the distance from the heating device 6 to the cold tandem rolling mill 8 is very short, there is not much problem even if the target temperature of the steel sheet S on the delivery side of the heating device 6 is set as the target temperature of the steel plate S heated by the heating device 6. do not have. On the other hand, if any one of the heating device 6, the thermometer 7, and the cold tandem rolling mill 8 is far away, until the steel plate S reaches the entry side of the cold tandem rolling mill 8, It is necessary to set the target temperature of the steel sheet S heated by the heating device 6 in consideration of the temperature drop of . However, from the viewpoint of environmental load, it is desirable that the amount of energy used for heating the steel sheet is small, and it is desirable that the heating device 6 and the thermometer 7 are placed as close to the cold tandem rolling mill 8 as possible.

Here, the inventors of the present invention investigated the fracture rate when a silicon steel sheet was cold-rolled by a tandem rolling mill having five stands. As a result, it was found that silicon steel sheets with a high Si content had a higher fracture rate than silicon steel sheets with a low Si content. In addition, as a result of investigating the cause of breakage, breakage on the upstream side such as #1std (hereinafter, the Nth stand from the upstream side in the conveying direction of the steel plate is denoted as "#Nstd"), #2std, etc., and #4std, etc. It was found that the cause was different from the breakage on the downstream side of #5std. In other words, fractures on the upstream side, especially those directly below #1 std and on the delivery side, are caused by local contraction of the steel plate shape such as belly stretch and edge stretch, and bending deformation by the threading roll and shape detector. It was estimated that The rolling reduction of #1 std is generally the highest among all the stands, and it is considered that a sudden change in the shape of the steel sheet is likely to cause breakage. In addition, as a result of further investigation on the rupture on the upstream side, the rupture rate (fracture occurrence rate) differs depending on the season. presumed to affect the rate. On the other hand, regarding the fracture on the downstream side, it was confirmed that edge cracks created in the stand on the upstream side progressed and led to fracture. For this reason, although the locations and causes of fractures are different, it was thought that all fractures could be suppressed by increasing the temperature of the steel sheet on the entry side of #1 std.

In order to verify the above conjecture, first, bending crack resistance was evaluated when bending strain was applied to a steel plate on a laboratory scale. This is because the resistance to bending cracking in this experiment is thought to be correlated with brittle fracture due to bending deformation at the sheet threading roll and the shape detector at the upstream stand described above. As test materials, the plate thickness is 2 mm, and the Si content is 1.8 mass%, 2.8 mass%, 3.3 mass%, and 3.7 mass% (hereinafter referred to as a silicon steel sheet with a Si content of Mmass% is referred to as “M% Si steel”) were annealed at 800° C. (corresponding to hot-rolled sheet annealing). Then, the silicon steel sheet after annealing was pickled, and a test material having a width of 24 mm and a length of 250 mm was cut out using a shearing machine. After that, both end faces were ground by 2 mm each to remove processing strain caused by shearing. This suppressed the occurrence of edge breakage. In an actual continuous cold rolling line, the 1.8% Si steel and the 2.8% Si steel are steel types in which brittle fracture is unlikely to occur. On the other hand, 3.3% Si steel and 3.7% Si steel are steel types in which brittle fracture occurs at a frequency of about several percent, especially in the upstream stand. Normally, in cold rolling, the steel sheet temperature at the entry side of the rolling mill is about the same as the temperature in the factory, and is around 15°C in winter.

Therefore, the temperature dependence of the bending crack resistance of silicon steel sheets was investigated when the steel sheet temperature was in the range of 15°C to 45°C. In this experiment, first, a steel plate with a thickness of 2 mm was rolled at a rolling reduction of 50% to produce a steel plate with a thickness of 1 mm. This simulates #1std. Next, the steel plate was passed through a roller leveler by simulating the bending deformation of the steel plate by a threading roll and a shape detector. Then, bending deformation was applied to the steel plate to evaluate bending crack resistance. The roller leveler has 11 upper and lower work rolls with a diameter of 50 mm, and the roll interval is 60 mm. An arbitrary value can be given to the bending stress on the surface of the steel sheet by changing the tightening amount of the upper work roll. In this experiment, the steel sheet temperature was changed in increments of 10° C. and the roll clamping amount was varied in increments of 0.5 mm, and the rupture limit of the steel sheet was arranged. It is considered that the larger the tightening amount at the time of breakage, the more difficult it is to break even in a cold rolling line. FIG. 2 shows the results obtained in this experiment. Considering the breakability in an actual continuous rolling mill, if the strip can be threaded without breaking up to a tightening amount of 4.0 mm under the conditions of this experiment, it is considered that the actual continuous rolling mill will not break. The target value for this experiment was that no breakage occurred at a loading depth of 4.0 mm.

As shown in FIG. 2, when compared with each Si content, the 1.8% Si steel did not break up to a tightening amount of 4.0 mm regardless of the temperature of the steel plate (15 to 45° C.). In the 2.8% Si steel, when the steel plate temperature was 15°C, breakage occurred at a tightening amount of 3.5 mm, but at 25°C or higher, breakage did not occur up to a tightening amount of 4.0 mm. In the 3.3% Si steel, fracture occurred at a tightening amount of 1.5 mm when the steel plate temperature was 15°C and at a tightening amount of 3.0 mm at 25°C. However, when the steel plate temperature was 35° C. or higher, no breakage occurred up to a tightening amount of 4.0 mm. In the 3.7% Si steel, fracture occurred at a tightening amount of 1.0 mm when the steel plate temperature was 15°C, 1.5 mm at 25°C, and 2.5 mm at 35°C. When the steel plate temperature was 45° C., no breakage occurred up to a tightening amount of 4.0 mm. As a result of the above experiment, it was confirmed that the Si content has a large effect on the fracture resistance of the steel sheet, and that the higher the Si content, the easier the steel sheet fractures. This agrees with the actual state of breakage in an actual continuous cold rolling mill. In particular, in the case of 3.3% Si steel and 3.7% Si steel, as a result of conducting experiments while changing the temperature of the steel plate, brittle fracture could be suppressed as the temperature increased.

FIG. 3 shows the result of estimating the steel plate temperature necessary for suppressing brittle fracture according to the Si content of the steel plate based on the results of this experiment. The approximation curve in the drawing is represented by the following formula (3). In this experiment, with the 1.8% Si steel, brittle fracture did not occur even at a steel plate temperature of 15° C. up to a tightening amount of 4.0 mm. However, with the 2.8% Si steel, when the steel plate temperature was 15°C, fracture occurred at a tightening amount of 3.5 mm. I think. Therefore, the value of the Si content α [%] in the formula (3) is practically considered to be about α>2. Further, the steel plate temperature T _Cmin calculated from the formula (3) is the minimum required temperature, and from the viewpoint of suppression of breakage, this temperature or higher is sufficient. However, if the steel sheet temperature becomes too high, the steel sheet shape and lubricity are affected, so the steel sheet temperature is set to 200° C. or less. Moreover, the upper limit of 4.5% of the Si content α was set from a range in which the temperature of the steel plate edge portion, which will be described later, is 200° C. or less.

Next, in order to suppress fractures caused by steel plate edge cracks, steel plates were rolled on a laboratory scale to evaluate the presence or absence of edge cracks. In this experiment, the edge crack that occurred on the upstream side in the rolling direction expanded and fractured as it progressed to the stand on the downstream side in the rolling direction. If it is possible to completely suppress the cracking of the edge of the steel sheet, it is possible to suppress the breakage due to the edge cracking. As test materials, four types of silicon steel plates, 1.8% Si steel, 2.8% Si steel, 3.3% Si steel, and 3.7% Si steel, each having a thickness of 2 mm, were cut to a width of 20 mm. and 250 mm long and annealed at 800° C. (equivalent to hot-rolled sheet annealing). Then, the silicon steel sheet after annealing was pickled. It can be considered that the state of the steel plate edge portion at this time is close to the actual state at the entry side of the continuous cold rolling mill.

In an actual continuous cold rolling line, the 1.8% Si steel is a steel type in which cracks at the steel plate edges are less likely to occur. On the other hand, 3.3% Si steel and 3.7% Si steel are steel types in which steel plate edge cracks occur at a frequency of about several percent. Normally, in cold rolling, the steel sheet temperature at the entry side of the rolling mill is about the same as the temperature in the factory, and is around 15°C in winter. Therefore, the temperature dependence of the edge crack resistance of silicon steel sheets was investigated when the steel sheet temperature was in the range of 15°C to 65°C. In this experiment, simulating #1std, the number of cracks (cracks of 1 mm or more) generated on both end faces (longitudinal direction) of the steel plate when a test material of w20 × L250 mm was rolled at a rolling reduction of 50%. The crackability was evaluated. The number of times of rolling at each Si amount and each temperature was 5 times, and the number of edge cracks was the average value of 5 times. Moreover, the steel plate temperature was made into the interval of 10 degreeC. FIG. 4 shows the results obtained in this experiment.

As shown in FIG. 4, when the steel sheet temperature was 15° C., no edge cracks occurred on both end surfaces of the 1.8% Si steel when compared with each Si content. In the 2.8% Si steel, seven edge cracks occurred in total on both end faces. In the 3.3% Si steel, 15 edge cracks occurred in total on both end faces, and in the 3.7% Si steel, 30 edge cracks occurred. When the steel plate temperature was 25° C., the total number of edge cracks on both end surfaces was 0 for both the 1.8% Si steel and the 2.8% Si steel. On the other hand, the 3.3% Si steel had 11 and the 3.7% Si steel had 27. When the steel plate temperature was 35° C., the total number of edge cracks on both end surfaces was 0 for the 1.8% Si steel and the 2.8% Si steel. On the other hand, in the 3.3% Si steel, a total of 5 edge cracks occurred in both end faces, and in the 3.7% Si steel, 20 edge cracks occurred. When the steel plate temperature was 45° C., the total number of edge cracks on both end surfaces was 0 for the 1.8% Si steel, the 2.8% Si steel, and the 3.3% Si steel. On the other hand, 10 edge cracks occurred in the 3.7% Si steel. When the steel plate temperature was 55° C., the total number of edge cracks on both end surfaces was 0 for the 1.8% Si steel, the 2.8% Si steel, and the 3.3% Si steel. On the other hand, 3 edge cracks occurred in the 3.7% Si steel. When the steel plate temperature is 65 ° C., the number of edge cracks on the total of both end faces is became 0. From the results of the above experiments, it was confirmed that the Si content has a large effect on the edge crack resistance, and that the higher the Si content, the more easily the steel plate edge cracks occur. This agrees with the reality of steel plate edge cracks in an actual continuous cold rolling mill.

FIG. 5 shows the result of estimating the temperature necessary for suppressing edge cracking of the steel sheet according to the Si content of the steel sheet based on the results of this experiment. The approximation curve in the drawing is represented by the following formula (4). In this experiment, with the 1.8% Si steel, even when the steel plate temperature was 15° C., no steel plate edge cracks occurred. However, for the 2.8% Si steel, when the steel plate temperature was 15° C., the steel plate edge cracks occurred. Therefore, the Si content α [%] in the formula (4) is practically considered to be about α>2. Further, the steel plate temperature T _Emin calculated from the formula (4) is the minimum required temperature, and from the viewpoint of suppression of breakage, this temperature or higher is sufficient. However, if the steel sheet temperature becomes too high, the steel sheet shape and lubricity are affected, so the steel sheet temperature is set to 200° C. or less. Moreover, the upper limit of 4.5% of the Si content α was set from the range in which the temperature of the steel plate edge portion calculated from the formula (4) is 200° C. or lower. The steel plate is heated within a range of 30 mm or more from the edge of the steel plate. This is because it is the influence range of width widening in cold rolling that affects steel plate edge cracks, and this range is said to be about 30 mm from the edge of the steel plate.

From the two experiments described above, it can be seen that the steel plate heating temperature required to suppress breakage from the center in the width direction of the steel plate and the breakage from the edge portion are different. For example, in the case of 3.7% Si steel, the temperature required to suppress breakage from the center in the width direction is 45°C or higher, and the temperature required to suppress edge cracking is 65°C or higher. As described above, in order to suppress the breakage of the silicon steel sheet, in addition to setting the amount of heating according to the Si content, the temperature of the edge portion is higher than that of the center portion in the width direction even for the same steel type. It was found that it was necessary to provide a temperature gradient in the width direction of the film, and the present invention was conceived. When a plurality of steel plates with different Si contents are conveyed by the same equipment, the heating device 6 acquires information indicating the Si content of the preceding material and the succeeding material, and sets the target temperature based on the information. Change, decide. Further, in the present embodiment, the material to be rolled is described as a silicon steel sheet, but the type of steel sheet is not limited. Steel sheets other than silicon steel sheets to which the technique of the present invention can be preferably applied include, for example, high-strength steel sheets and high-alloy steel sheets.

As described above, according to the cold-rolled steel strip manufacturing facility and manufacturing method according to the embodiment of the present invention, by using the full-width heating device 4 and the edge heating device 5 together, By appropriately controlling the temperature necessary for suppressing the breakage of the steel sheet and edge cracking, the breakage of the steel sheet is suppressed. Therefore, according to the cold-rolled steel strip manufacturing facility and the cold-rolled steel strip manufacturing method according to one embodiment of the present invention, when the silicon steel sheet is cold-rolled, breakage of the steel sheet is suppressed with the minimum necessary energy. Therefore, the silicon steel sheet can be stably cold rolled with minimum environmental load.

An example showing the effects of the present invention will be described. In this embodiment, a full width heating device and an edge heating device are installed on the entry side of the cold rolling mill in this order from the upstream side in the rolling direction, so that the steel plate temperature on the entry side of the rolling mill can be set to an arbitrary temperature. ing. Then, it was finished to a predetermined thickness by a 5-stand cold tandem rolling mill. All of the steel types used in this example were silicon steel sheets, which were divided into three groups according to the Si content. Specifically, there are three groups: a group with a Si content of 1.0 mass% to 2.0 mass%, a group with a Si content of 2.0 mass% to 3.0 mass%, and a group with a Si content of 3.0 mass% to 3.5 mass%. Each group has a thickness of 1.8 mm to 2.4 mm before rolling and a thickness of 0.3 mm to 0.5 mm after rolling. In order to investigate the rupture rate due to the difference in Si content, care was taken so that the plate thickness was not uneven among the groups. The breaking rate of 200 coils was investigated in each group. The outside air temperature (the temperature inside the factory) was about 15°C. Table 1 shows the coils and conditions investigated. The steel plate temperature was measured using a thermometer installed at the entrance side of the rolling mill.

[Reference example]
An example is shown in which the steel plate is not heated by the full-width heating device and the edge heating device, that is, the steel plate temperature at the entry side of the rolling mill is about 15°C. The rupture rate of 200 coils with a Si content of 1.0 mass% to 2.0 mass% was 0%. On the other hand, the rupture rate of 200 coils with an Si content of 2.0 mass% to 3.0 mass% was 1%, and the rupture rate of 200 coils with an Si content of 3.0 mass% to 3.5 mass% was 3%.

[Invention Example 1]
The steel plate temperature at the entry side of the cold tandem rolling mill was calculated according to the Si content of the silicon steel plate from the above formulas (1) and (2), and based on this, the steel plate was heated by the full width heating device and the edge heating device. An example case is shown. This is the case of the configuration in which the order is the full width heating device, the edge heating device, and the cold tandem rolling mill. Also, the distance between the cold tandem rolling mill and the heating device is 10 m. In the example of the present invention, the temperature of the edge portion is higher than that of the central portion of the width of the steel sheet. The rupture rate of 200 coils (width center 17° C., edge portion 18° C.) having an Si content of 1.0 mass % to 2.0 mass % was 0%. In addition, the fracture rate of 200 coils with Si content of 2.0 mass% to 3.0 mass% (width center 30 ° C., edge portion 35 ° C.) is also 0%, 200 coils with Si content of 3.0 mass% to 3.5 mass% (width The fracture rate at the center (45°C, edge portion 60°C) was also 0%. It was confirmed that by heating the silicon steel sheet according to the present invention, breakage of the steel sheet can be greatly reduced.

[Invention Example 2]
The steel plate temperature at the entry side of the cold tandem rolling mill was calculated according to the Si content of the silicon steel plate from the above formulas (1) and (2), and based on this, the steel plate was heated by the full width heating device and the edge heating device. An example case is shown. This is the case of the configuration in which the order is the edge portion heating device, the full width heating device, and the cold tandem rolling mill. That is, the invention example 1 is an embodiment that differs only in the arrangement order of the full-width heating device and the edge portion heating device. The rupture rate of 200 coils (width center 17° C., edge portion 18° C.) having an Si content of 1.0 mass % to 2.0 mass % was 0%. In addition, the fracture rate of 200 coils with Si content of 2.0 mass% to 3.0 mass% (width center 30 ° C., edge portion 35 ° C.) is also 0%, 200 coils with Si content of 3.0 mass% to 3.5 mass% (width The fracture rate at the center (45°C, edge portion 60°C) was also 0%. It has been confirmed that when the steel plate temperature calculated by the above formulas (1) and (2) can be secured at the entry side of the cold tandem rolling mill, the steel plate breakage can be suppressed regardless of the order of the full width heating device and the edge heating device. rice field.

[Invention Example 3]
The steel plate temperature at the entry side of the cold tandem rolling mill was calculated according to the Si content of the silicon steel plate from the above formulas (1) and (2), and based on this, the steel plate was heated by the full width heating device and the edge heating device. An example case is shown. This is the case where the heating device is installed so that the distance between the cold tandem rolling mill and the heating device is between 1 m and 1.5 m. That is, the distance between the cold tandem rolling mill and the heating device is shorter than in Invention Example 1, and the other conditions are the same as in Invention Example 1. The rupture rate of 200 coils (width center 17° C., edge portion 18° C.) having an Si content of 1.0 mass % to 2.0 mass % was 0%. In addition, the fracture rate of 200 coils with Si content of 2.0 mass% to 3.0 mass% (width center 30 ° C., edge portion 35 ° C.) is also 0%, 200 coils with Si content of 3.0 mass% to 3.5 mass% (width The fracture rate at the center (45°C, edge portion 60°C) was also 0%. Focusing only on the fracture rate, fracture can be suppressed up to 3.5% Si steel, which is the same as Invention Example 1, but from the viewpoint of energy consumption, it can be significantly reduced compared to Invention Example 1. , and the superiority of Invention Example 3 can be confirmed. Therefore, from the viewpoint of energy consumption reduction (environmental resistance), it was confirmed that the closer the distance between the cold tandem rolling mill and the heating device, the more desirable.

[Invention Example 4]
The steel plate temperature at the entry side of the cold tandem rolling mill was calculated according to the Si content of the silicon steel plate from the above formulas (1) and (2), and based on this, the steel plate was heated by the full width heating device and the edge heating device. An example case is shown. Here, a transverse induction heating device is used. That is, this is an example in which, of the conditions of Example 1, the full width heating device was changed from the solenoid type induction heating device to the transverse type induction heating device. The rupture rate of 200 coils (width center 17° C., edge portion 18° C.) having an Si content of 1.0 mass % to 2.0 mass % was 0%. In addition, the fracture rate of 200 coils with Si content of 2.0 mass% to 3.0 mass% (width center 30 ° C., edge portion 35 ° C.) is also 0%, 200 coils with Si content of 3.0 mass% to 3.5 mass% (width The fracture rate at the center (45°C, edge portion 60°C) was also 0%. It was confirmed that the full-width heating device can obtain the same fracture suppression effect for the solenoid type and the transverse type.

[Comparative Example 1]
An example in which the edge heating device is not used and only the full width heating device is used is shown. The temperature of the steel sheet heated by the full-width heating device was calculated from Equation (1). In other words, the temperature required to suppress edge cracking cannot be secured, and the steel sheet temperature at the edge tends to drop more easily than at the center of the width, so the temperature at the edge is lower than that at the center of the width. ing. The rupture rate of 200 coils (width center 17° C., edge portion 16° C.) having an Si content of 1.0 mass % to 2.0 mass % was 0%. On the other hand, the rupture rate of 200 coils (width center 30° C., edge portion 25° C.) with Si content of 2.0 mass% to 3.0 mass% is 0.5%, 3.0 mass% to 3.5 mass% 200 The breaking rate of the coil (width center 45°C, edge portion 35°C) was 2%. When the rupture mode of the ruptured coil was investigated, it was found that rupture from the center in the width direction could be suppressed, but rupture due to edge cracking could not be suppressed.

[Comparative Example 2]
An example in which the edge heating device is not used and only the full width heating device is used is shown. The temperature of the steel sheet heated by the full-width heating device was calculated from Equation (2). In other words, the entire widthwise region is heated so that the temperature of the edge portion reaches the temperature considered necessary for suppressing cracking of the edge portion. The rupture rate of 200 coils (width center 20°C, edge portion 18°C) with Si content of 1.0 mass% to 2.0 mass% was 0%. In addition, the rupture rate of 200 coils (width center 40 ° C., edge portion 35 ° C.) with Si content of 2.0 mass% to 3.0 mass% is 0%, 200 coils (width 3.0 mass% to 3.5 mass%) The fracture rate at the center (70°C, edge portion 60°C) was also 0%. However, the temperature of the central portion in the width direction is heated more than necessary from the viewpoint of suppressing breakage, and it is desirable to reduce the input energy amount when considering the environmental load.

[Comparative Example 3]
An example of using only the edge heating device without using the full width heating device is shown. The temperature of the edge portion of the steel sheet heated by the edge portion heating device was calculated from Equation (2). The rupture rate of 200 coils (width center 15° C., edge portion 18° C.) having an Si content of 1.0 mass % to 2.0 mass % was 0%. On the other hand, the rupture rate of 200 coils with Si content of 2.0 mass% to 3.0 mass% (width center 15 ° C., edge portion 35 ° C.) is 0.5%, 3.0 mass% to 3.5 mass% 200 The fracture rate of the coil (width center 15°C, edge portion 60°C) was 2%. When the rupture mode of the ruptured coil was investigated, it was found that rupture due to edge cracking could be suppressed, but rupture from the central portion in the width direction could not be suppressed.

[Comparative Example 4]
The steel plate temperature at the entry side of the cold tandem rolling mill was calculated according to the Si content of the silicon steel plate from the above formulas (1) and (2), and based on this, the steel plate was heated by the full width heating device and the edge heating device. An example case is shown. This is the case where the distance between the heating device and the cold tandem rolling mill is 20 m. That is, this is an example in which the distance between the heating device and the cold tandem rolling mill was increased among the conditions of Invention Example 1. Since the distance between the heating device and the cold tandem rolling mill is long, even if the upper limit of the capacity of the heating device is used, the steel plate temperature on the entry side of the cold tandem rolling mill calculated from the above formulas (1) and (2) is maintained. I couldn't. The rupture rate of 200 coils with a Si content of 1.0 mass% to 2.0 mass% (width center 15 ° C., edge portion 15 ° C.) is 0%, and the Si content of 200 coils with a Si content of 2.0 mass% to 3.0 mass% The fracture rate at (width center 25°C, edge portion 30°C) was also 0%. On the other hand, the fracture rate of 200 coils (width center 40° C., edge portion 50° C.) of 3.0 mass % to 3.5 mass % was 1%. It is desirable that the distance between the heating device and the cold tandem rolling mill is as short as possible. It was confirmed that when installed, the higher the Si steel, the more likely it is to break.

[Comparative Example 5]
The steel plate is heated by a full-width heating device and an edge heating device so that the steel plate temperature at the entry side of the rolling mill is about 30% lower than the steel plate temperature at the entry side of the rolling mill according to the Si content of the silicon steel plate calculated from the above formulas (1) and (2). shows an example of heating. Other conditions are the same as in Invention Example 1. The rupture rate of 200 coils with a Si content of 1.0 mass% to 2.0 mass% (width center 15 ° C., edge portion 15 ° C.) is 0%, and 200 coils with a Si content of 2.0 mass% to 3.0 mass% (width center 20 ℃, edge portion 25 ℃) was also 0%. On the other hand, the rupture rate of 200 coils (width center 30° C., edge portion 40° C.) having a Si content of 3.0 mass % to 3.5 mass % was 1.5%. It was confirmed that when the steel plate temperature is lower than the steel plate temperature calculated from the above formulas (1) and (2), the higher the Si steel, the more likely it is to break.

As described above, it was confirmed that by applying the present invention and heating the steel sheet on the entry side of the cold tandem rolling mill, it is possible to suppress breakage of the steel sheet. In particular, in the case of a silicon steel sheet having a Si content of 3 mass% or more, heating the steel sheet to an appropriate temperature can greatly reduce the breakage of the steel sheet, so that productivity and yield can be improved. can be done.

As described above, the cold-rolled steel strip manufacturing facility and the cold-rolled steel strip manufacturing method according to the present invention have been specifically described with the embodiments and examples for carrying out the invention. It should not be limited and should be interpreted broadly based on the scope of the claims. In addition, it goes without saying that various changes and modifications based on these descriptions are also included in the gist of the present invention.

REFERENCE SIGNS LIST 1 payoff reel 2 joining device 3 looper 4 full width heating device 5 edge heating device 6 heating device 7 thermometer 8 cold tandem rolling mill 9 cutting machine 10 tension reel S steel plate

Claims (12)

A full width heating device that heats the steel plate over the entire width direction of the steel plate, an edge heating device that heats the width direction end portions of the steel plate, and a downstream side in the rolling direction with respect to the full width heating device and the edge heating device A method for manufacturing a cold-rolled steel sheet using a cold rolling mill for rolling the steel sheet, wherein
A step of heating the steel sheet using the full width heating device and the edge heating device so that the temperature of the width direction end portion of the steel plate is higher than the temperature of the width direction center portion of the steel plate on the entry side of the cold rolling mill. A method for producing a cold-rolled steel sheet, comprising: The production of the cold-rolled steel sheet according to claim 1, wherein the temperatures of the widthwise central portion and the widthwise end portions of the steel sheet on the entry side of the cold rolling mill vary according to the Si content of the steel sheet. Method. The temperature of the widthwise center and the widthwise end of the steel sheet on the entry side of the cold rolling mill is the temperature calculated by the following formulas (1) and (2) that change depending on the Si content α. The method for manufacturing a cold-rolled steel sheet according to claim 1 or 2.

A full width heating step of heating the steel plate over the entire width direction of the steel plate by the full width heating device, an edge portion heating step of heating the width direction end portion of the steel plate by the edge portion heating device, and a steel plate by the cold rolling mill 4. The method for producing a cold-rolled steel sheet according to any one of claims 1 to 3, wherein a rolling step of rolling is performed in this order. An edge heating step of heating the ends of the steel plate in the width direction by the edge heating device, a full width heating step of heating the steel plate over the entire width direction of the steel plate by the full width heating device, and a steel plate by the cold rolling mill. 4. The method for producing a cold-rolled steel sheet according to any one of claims 1 to 3, wherein a rolling step of rolling is performed in this order. a full-width heating device that heats the steel plate over the entire width of the steel plate;
an edge portion heating device for heating the width direction end portion of the steel plate;
a cold rolling mill for rolling the steel plate, which is disposed on the downstream side in the rolling direction with respect to the full width heating device and the edge heating device,
The full width heating device and the edge heating device heat the steel plate so that the temperature of the widthwise end portion of the steel plate is higher than the temperature of the widthwise central portion of the steel plate on the entrance side of the cold rolling mill. manufacturing facilities for cold-rolled steel sheets. The full width heating device and the edge heating device change the temperature of the width direction central portion and the width direction end portion of the steel plate on the entry side of the cold rolling mill according to the Si content of the steel plate. Equipment for manufacturing the cold-rolled steel sheet according to claim 6. The following formula (1), ( 8. The cold-rolled steel sheet manufacturing facility according to claim 6 or 7, wherein heating is performed to the temperature calculated in 2).

The full width heating device and the edge heating device according to any one of claims 6 to 8, characterized in that they are installed at a position within 10 m from the entry side of the cold rolling mill. Manufacturing equipment for cold-rolled steel sheets. The cold-rolled steel sheet manufacturing facility according to any one of claims 6 to 9, wherein the full-width heating device is a solenoid induction heating device. The cold rolling apparatus according to any one of claims 6 to 10, wherein the full width heating device and the edge heating device are arranged in this order from the upstream side in the rolling direction of the cold rolling mill. Rolled steel sheet manufacturing equipment. The cold rolling apparatus according to any one of claims 6 to 10, wherein the edge heating device and the full width heating device are arranged in this order from the upstream side of the cold rolling mill in the rolling direction. Rolled steel sheet manufacturing equipment.

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